Liners are frequently hung on casing using liner hangers. The liner hangers have slips for anchoring support for the liner string that are extended radially. The leading end of each slip has a serrated leading face that is designed to penetrate the surrounding casing wall for a grip. The slips are generally individual segments that are edge guided in a conforming recess in a slip body. The edge guiding is in effect an angled ramp so that as the slips move axially they also extend radially. The force to initiate the slip movement can be a potential energy force such as a spring force that is held during run in and then released to act on each slip to move the slip in an uphole direction along the supporting edge ramps. Following the extension of the slips the weight of the liner can be released from a running string for full support on the surrounding casing. A seal is usually associated with the liner hanger and is generally set after the liner is cemented.
When the slips contact the surrounding casing a radial reaction force ensues from the casing and into the extended slip. That radial force is then transmitted to the slip housing in a circumferential direction. This slip design is well known and is illustrated in U.S. Pat. No. 7,546,872 (FIG. 9); U.S. Pat. No. 6,431,277 (FIGS. 37 and 38); U.S. Pat. No. 5,086,845 (FIG. 3) and U.S. Pat. No. 4,711,326.
At some predetermined loading when the slips are extended into the surrounding casing and the weight of the liner is transferred to the slips the side walls of the slip housing that abut the slips on opposed ends to guide them axially and radially begin to yield indicating a limiting condition for the load that can be supported. The present invention addresses this limit and with a simple modification seeks to alter the nature of the loading between the casing and the liner string supported of it by the slips. In essence, the traditional force orientation of the known designs comprising a radial reaction force into each slip that then goes into the slip housing circumferentially is changed by having a portion of the slip body contact the top of the extended slip that has already been extended into engagement with the surrounding casing. What then happens is that the weight of the liner string is transferred predominantly axially from the slip body into the engaged slip in a substantially axial direction so that the reaction force from the casing is in an opposite axial direction. This reduces slip housing distortion at opposed sides of each slip and allows a greater support capacity for the slips without substantial engineering revision from the configuration of the existing designs making retrofits possible. The load capacity for a given size is greatly enhanced. In an improvement of this design the end of the slip has a broader dimension than the balance of the slip body to reduce contact stress and to allow the use of a thinner slip which in turn allows higher mandrel pressure rating to be used in a given surrounding tubular. The broadened lower end also features edge undercuts to promote fluid flow past the set slips and the slip housing is also formed with flow slots for enhancement of flow past the set slips. The load carrying capacity increase with the addition of the wings on the end is in the order of 50%. These and other aspects of the present invention will be more readily apparent to those skilled in the art by reviewing the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.